The euro rocketed to a two-month high of $1.29 and sterling jumped two cents to almost $1.54 after the Fed confessed that the US economy may not recover for five or six years. Far from winding down emergency stimulus, the bank may need a fresh blast of bond purchases or quantitative easing.

Usually the dollar serves as a safe haven whenever the world takes fright, and there was plenty of sobering news from China and other quarters on Thursday. Not this time. The US itself has become the problem.

“The worm is turning,” said David Bloom, currency chief at HSBC. “We’re in a world of rotating sovereign crises. The market seems to become obsessed with one idea at a time, then violently swings towards another. People thought the euro would break-up. Now we’re moving into a new phase because we’re hearing alarm bells of a US double dip.”

Mr Bloom said a deep change is under way in investor psychology as funds and central banks respond to the blizzard of shocking US data and again focus on the fragility of an economy where public debt is surging towards 100pc of GDP, not helped by the malaise enveloping the Obama White House. “The Europeans have aired their dirty debt in public and taken some measures to address it, whilst the US has not,” he said.

The Fed minutes warned of “significant downside risks” and a possible slide into deflation, an admission that zero interest rates, $1.75 trillion of QE, and a fiscal deficit above 10pc of GDP have so far failed to lift the economy out of a structural slump.

“The Committee would need to consider whether further policy stimulus might become appropriate if the outlook were to worsen appreciably,” it said. The economy might not regain its “longer-run path” until 2016.

“The Fed is throwing in the towel,” said Gabriel Stein, of Lombard Street Research. “They are preparing to start QE again. This was predictable because the M3 broad money supply has been contracting for months.”

The Fed minutes amount to a policy thunderbolt, evidence of how quickly the recovery has lost steam. Just weeks ago the Fed was mapping out withdrawal of stimulus.

Goldman Sachs said it expects the euro to rise to $1.35 by the end of the year. The yen will appreciate to ¥83, through the pain barrier for most of Japan’s big exporters. The new twist is that SAFE, China’s $2.4 trillion fund, has begun buying record amounts of Japanese bonds, a shift in reserve allocation away from the dollar.

The signs of a deep and sudden slowdown in the US are becoming ever clearer as the “sugar rush” from the Obama fiscal stimulus wears off and the inventory boost fades. California, Illinois and other states are cutting spending, tightening US fiscal policy by 0.8pc of GDP.

Thursday’s plunge in the Philadelphia Fed’s July index of new manufacturing orders to –4.3 suggests that the economy may have buckled abruptly, as it did in mid-2008. The Economic Cycle Research Institute’s ECRI leading indicator has tumbled, reaching –8.3pc last week. This points to a sharp slowdown or recession within three months.

While US port data looked buoyant in June, the details were troubling. Outbound traffic from Long Beach fell from 139,000 containers in May to 116,000 in June. Shipments from Los Angeles fell from 161,000 to 155,000. This drop in exports is worsening the US trade deficit, eroding the dollar.

The US workforce has shrunk by a 1m over the past two months as discouraged jobless give up the hunt. Retail sales have fallen for the past two months. New homes sales crashed to 300,000 in May after tax credits ran out, the lowest since records began in 1963. Mortgage applications have fallen by 42pc to 13-year low since April. Paul Dales at Capital Economics said the “shadow inventory” of unsold properties has risen to 7.8m. “The double dip in housing has begun,” he said.

Alcoa, CSX, Intel, and JP Morgan have reported good earnings, but they mostly did so in July 2008 just before their shares collapsed. Such earnings rarely catch turning points and can be a lagging indicator. Profits have been boosted in this cycle by cost-cutting, which is self-defeating for the economy as a whole.

The minutes confirm the Fed is split down the middle over QE. Fed watchers say the Board in Washington wants to be ready to launch another round of bond purchases if necessary, pushing the banks balance sheet from $2.4 trillion towards $5 trillion, but hawks at the regional banks are highly sceptical.

A study by the San Francisco Fed said the interest rates need to be –4.5pc to stabilise the economy under the Fed’s “rule of thumb”. Since this is impossible, massive QE needs to make up the difference.

Tim Congdon from International Monetary Research said the US authorities have botched policy response. “They are forcing banks to contract lending by raising their capital asset ratios. They have let M3 shrink by 1pc a month, as in the early 1930s. The solution is simple. The Fed must raise the level of deposits by purchasing bonds from the non-banking system as the Bank of England has done. They refuse to do it,” he said.